1. Field of the Invention
The present invention relates to diode pumped heat capacity lasers. More specifically, it relates to the production of high-energy laser output from a liquid state laser operated in a heat capacity limited regime.
2. Description of Related Art
For continuous operation of medium to high average power lasers various heat exchanger systems, frequently with water flow loops and refrigeration units, have been used to handle the waste heat These cooling systems tend to be a significant (if not dominant) contribution to the laser system's mass, size, and average power consumption. There are a class of laser applications arising today that require minimal mass, volume, and peak electrical demand to support a given laser power. In this class there are a variety of applications in which the laser is to be operated only for an interval of time, followed by a longer period of time in which system recovery may be achieved; the so called “burst mode” laser. This is the basis of the concept of the heat capacity laser solid-state media (See U.S. Pat. No. 5,526,372, titled: “High Energy Bursts From A Solid State Laser Operated In The Heat Capacity Limited Regime,” by Albrecht et al.). In the state of the art solid-state heat capacity system, the heat released during operation is stored in the lasing media itself, which is also thermally isolated. This isolation is used to reduce thermal gradients within the laser media. If allowed to form, these gradients severely limit the optical quality of the laser media.
Laser systems empowered by heat capacity technology have a high value at the present time. Practical laser weapons are militarily desirable. The systems receiving attention are heat capacity solid-state lasers. The solid-state heat capacity approach solves a variety of problems that the conventionally cooled laser poses when operated in the extremely high power regime. A thermally isolated media can be pumped much harder than a cooled media since there is so little heat conduction in the media, hence greatly reduced internal stresses (driven by temperature gradients). With greatly reduced thermal gradients, there are greatly reduced beam aberrations, which allow current adaptive optical technology to handle the residual distortions even in a 100,000 watt scale laser. A 100 kW actively cooled laser would need ˜400 kW worth of cooling on the gain media. This will produce a very large concurrent power drain to the refrigeration unit as well require a big and heavy cooling unit This prevents the practical realization of mobile applications. In the heat capacity approach, cooling is separate from lasing, such that the cooling rate does not need to match the lasing media heating rate, allowing much smaller cooling systems and requiring power for cooling after the high laser power demand is gone.
A heat capacity laser is not simply a laser running with the cooling off. A heat capacity laser must be built according to principles laid out in the description of heat capacity lasers as explained in U.S. Pat. No. 5,526,372 For solid-state systems, the amount of gain media is more dependent on run time than on lasing cross section. Structures to hold the media must be reasonably thermally isolating in order to keep thermal conduction small. The on time will be dictated by the elevated temperature laser dynamics. The pumping scheme must be very uniform in the lasing beam cross-section plane.